Circuit for indicating power level over a communication interface

Abstract

A power classification circuit is provided. The circuit includes a control circuit, a current sensor, and an indicator signal, and a voltage source. The control circuit is configured to control the voltage source to provide a first predetermined classification voltage, detect a first classification current, provide a predetermined indexing voltage, and control the at least one voltage source to provide a second predetermined classification voltage and detect a second classification current. The control circuit is configured to detect the first classification current within a classification current range, detect a draw down current outside of the classification current range, and detect the second classification current within the classification current range. The control circuit is further configured to set the indicator signal to a first predetermined state indicating a power type based on the detected first classification current, draw down current, and the second classification current.

We claim:  
     
         1 . A power classification circuit, comprising:
 a control circuit;   a current sensor coupled to the control circuit; and   at least one voltage source coupled to the control circuit, wherein the control circuit is configured to, in sequence:
 control the at least one voltage source to provide a first predetermined classification voltage and in response:
 detect, by the current sensor, a first classification current; 
 
 control the at least one voltage source to provide a predetermined indexing voltage; and 
 control the at least one voltage source to provide a second predetermined classification voltage and in response:
 detect, by the current sensor, a second classification current; 
 
   wherein the control circuit, responsive to the current sensor, is configured to:
 detect the first classification current within a classification current range defined by a lower classification current limit and upper classification current limit; 
 detect, after detecting the first classification current, a draw down current outside of the classification current range; and 
 detect, after detecting the draw down current, the second classification current within the classification current range, wherein the control circuit is further configured to set an indicator signal to a first predetermined state indicating a power type based on the detected first classification current, draw down current and the second classification current. 
   
     
     
         2 . The power classification circuit of  claim 1 , wherein the predetermined indexing voltage is out of a classification voltage range defined by a lower classification voltage limit and a higher classification voltage limit. 
     
     
         3 . The power classification circuit of  claim 1 , wherein the at least one voltage source provides the predetermined indexing voltage for a sufficient time for the predetermined indexing voltage to stabilize and be recognized by a powered device coupled to the power classification circuit. 
     
     
         4 . The power classification circuit of  claim 1 , wherein the second classification current represents a circularly adjacent valid classification value to the first classification current, wherein when the first classification current does not represent a valid classification value of four, the second classification current represents the next higher valid classification value than the first classification value, wherein when the first classification current represents a valid classification value of four, the second classification current represents a valid classification value of one. 
     
     
         5 . The power classification circuit of  claim 1 , wherein the second classification current represents a circularly adjacent valid classification value to the first classification current, wherein when the first classification current does not represent a valid classification value of one, the second classification current represents the next lower valid classification value than the first classification value, wherein when the first classification current represents a valid classification value of one, the second classification current represents a valid classification value of four. 
     
     
         6 . The power classification circuit of  claim 1 , further comprising:
 a detection circuit,   wherein the detection circuit is configured to detect a powered device coupled to the power classification circuit prior to the at least one voltage source providing a first predetermined classification voltage.   
     
     
         7 . The power classification circuit of  claim 1 , wherein the second predetermined classification voltage represents an adjacent valid classification value to the first predetermined classification voltage. 
     
     
         8 . The power classification circuit of  claim 1 , wherein subsequent to the current sensor detects the second classification current, the control circuit enables the at least one voltage source to provide a predetermined signature voltage. 
     
     
         9 . The power classification circuit of  claim 8 , wherein if the first classification current is equal to the second classification current, the control circuit sets the indicator signal to indicate a low power type, wherein if the first classification current is not equal to the second classification current or the current sensor detects a signature current in response to the predetermined signature voltage, the control circuit sets the indicator signal to indicate a high power type. 
     
     
         10 . The power classification circuit of  claim 1 , wherein a power sourcing equipment (PSE) comprises the power classification circuit. 
     
     
         11 . The power classification circuit of  claim 10 , wherein the PSE allocates power responsive to the determined classification. 
     
     
         12 . A control device, comprising:
 a control circuit;   a current sensor coupled to the control circuit; and   a voltage source coupled to the control circuit;   wherein the control circuit is configured to:
 enable the voltage source to provide a first classification voltage for a first classification cycle time, wherein the first classification voltage is within a classification voltage range defined by a lower classification voltage limit and an upper classification voltage limit; 
 measure a first classification current, from the current sensor, in response to providing the first classification voltage; 
 subsequent to the first classification cycle time, enable the voltage source to provide a voltage outside of the classification voltage range for a classification indexing time; 
 subsequent to the classification indexing time, enable the voltage source to provide a second classification voltage for a second classification cycle time, wherein the second classification voltage is within the classification voltage range; 
 measure a second classification current, from the current sensor, in response to providing the second classification voltage; and 
 determine a classification responsive to the first classification current and the second classification current. 
   
     
     
         13 . The control device of  claim 12 , wherein the lower classification voltage limit is 15.5 volts and the upper classification voltage limit is 20.5 volts. 
     
     
         14 . The control device of  claim 12 , wherein a power sourcing equipment (PSE) comprises the control device. 
     
     
         15 . The control device of  claim 14 , wherein the PSE allocates power responsive to the determined classification. 
     
     
         16 . The control device of  claim 12 , wherein the second classification current represents a circularly adjacent valid classification value to the first classification current, wherein when the first classification current does not represent a valid classification value of four, the second classification current represents the next higher valid classification value than the first classification value, wherein when the first classification current represents a valid classification value of four, the second classification current represents a valid classification value of one. 
     
     
         17 . The control device of  claim 12 , wherein the second classification current represents a circularly adjacent valid classification value to the first classification current, wherein when the first classification current does not represent a valid classification value of one, the second classification current represents the next lower valid classification value than the first classification value, wherein when the first classification current represents a valid classification value of one, the second classification current represents a valid classification value of four. 
     
     
         18 . The control device of  claim 12 , wherein subsequent to the second classification cycle time, the control circuit enables the voltage source to provide a signature voltage for a signature cycle time, wherein the signature voltage is below the classification voltage range. 
     
     
         19 . The control device of  claim 18 , wherein subsequent to the voltage source providing the signature voltage the control circuit measures a signature current from the current sensor and identifies a powered device associated with the signature current as a high power device. 
     
     
         20 . The control device of  claim 18 , wherein subsequent to the signature cycle time, the control circuit enables the voltage source to provide an operating voltage. 
     
     
         21 . The control device of  claim 18 , wherein the control device is incorporated within a Power Sourcing Equipment (PSE), and wherein in the event that a powered device (PD) coupled to the PSE does not detect the signature voltage, the control circuit identifies the power sourcing equipment as a low power source. 
     
     
         22 . The control device of  claim 12 , wherein the first classification current has a different value than the second classification current. 
     
     
         23 . The control device of  claim 22 , wherein the different values of the classification current are responsive to the voltage outside of the classification voltage range for the classification indexing time. 
     
     
         24 . A power classification circuit, comprising:
 a control circuit;   a current sensor coupled to the control circuit; and   at least one voltage source coupled to the control circuit, wherein the control circuit is configured to, in sequence:
 control the at least one voltage source to provide a first predetermined classification voltage and in response:
 detect, by the current sensor, a first classification current within a classification current range defined by a lower classification current limit and upper classification current limit; and 
 detect, by the current sensor, a draw down current outside of the classification current range; 
 
 control the at least one voltage source to provide a predetermined indexing voltage; 
 control the at least one voltage source to provide a second predetermined classification voltage and in response: 
 detect, by the current sensor, a second classification current within the classification current range; and 
 set an indicator signal to a first predetermined state indicating a power type based on the detected first classification current, draw down current and the second classification current. 
   
     
     
         25 . The power classification circuit of  claim 24 , wherein the predetermined indexing voltage is out of a classification voltage range defined by a lower classification voltage limit and a higher classification voltage limit. 
     
     
         26 . The power classification circuit of  claim 24 , wherein the at least one voltage source provides the predetermined indexing voltage for a sufficient time for the predetermined indexing voltage to stabilize and be recognized by a powered device (PD) coupled to the power classification circuit. 
     
     
         27 . The power classification circuit of  claim 24 , wherein the second classification current represents a circularly adjacent valid classification value to the first classification current, wherein when the first classification current does not represent a valid classification value of four, the second classification current represents the next higher valid classification value than the first classification value, wherein when the first classification current represents a valid classification value of four, the second classification current represents a valid classification value of one. 
     
     
         28 . The power classification circuit of  claim 24 , wherein the second classification current represents a circularly adjacent valid classification value to the first classification current, wherein when the first classification current does not represent a valid classification value of one, the second classification current represents the next lower valid classification value than the first classification value, wherein when the first classification current represents a valid classification value of one, the second classification current represents a valid classification value of four. 
     
     
         29 . The power classification circuit of  claim 24 , further comprising:
 a detection circuit,   wherein the detection circuit is configured to detect a powered device coupled to the power classification circuit prior to the at least one voltage source providing a first predetermined classification voltage.   
     
     
         30 . The power classification circuit of  claim 24 , wherein the second predetermined classification voltage represents an adjacent valid classification value to the first predetermined classification voltage. 
     
     
         31 . The power classification circuit of  claim 24 , wherein subsequent to the current sensor detects the second classification current, the control circuit enables the at least one voltage source to provide a predetermined signature voltage. 
     
     
         32 . The power classification circuit of  claim 31 , wherein if the first classification current is equal to the second classification current, the control circuit sets the indicator signal to indicate a low power type, wherein if the first classification current is not equal to the second classification current or the current sensor detects a signature current in response to the predetermined signature voltage, the control circuit sets the indicator signal to indicate a high power type. 
     
     
         33 . The power classification circuit of  claim 24 , wherein a power sourcing equipment (PSE) comprises the power classification circuit. 
     
     
         34 . The power classification circuit of  claim 33 , wherein the PSE allocates power responsive to the determined classification.